Planar lighting device

Abstract

A planar lighting device comprises: a light guide plate including a concave rectangular light exit plane, two light entrance planes containing two opposite sides of the light exit plane and disposed opposite each other, two symmetrical inclined planes opposing to the light exit plane such that their distance from the light exit plane increases with the increasing distance from the two light entrance planes toward the center of the light exit plane, a curved portion connecting the two inclined planes; two light sources respectively disposed opposite the two light entrance planes for emitting light to enter the light into the light guide plate through the light entrance planes; and sliding mechanisms allowing the light sources to slide in a direction parallel to the light entrance planes of the light guide plate to absorb the expansion and contraction of the light sources along the length thereof.

1. A planar lighting device comprising:
 a light guide plate including a concave rectangular light exit plane, two light entrance planes containing two opposite sides of the light exit plane and disposed opposite each other, two symmetrical inclined planes opposing to the light exit plane such that their distance from the light exit plane increases with the increasing distance from the two light entrance planes toward the center of the light exit plane, a curved portion connecting the two inclined planes, and light scattering particles for scattering light that propagates inside the light guide plate; 
 two light sources respectively disposed opposite the two light entrance planes for emitting light to enter the light into the light guide plate through the light entrance planes; 
 holder means for supporting and integrating each light source and the light guide plate while keeping their mutual distance constant; 
 a housing for accommodating the light sources and the light guide plate integrated by the holder means; and 
 sliding mechanisms allowing the light sources to slide in a direction parallel to the light entrance planes of the light guide plate to absorb the expansion and contraction of the light sources along the length thereof, 
 wherein the sliding mechanisms each comprise pins provided on the housing engaged in long holes formed in the light source so as to be long in the direction parallel to the light entrance planes. 
 
     
     
       2. The planar lighting device of  claim 1 , wherein the holder means integrates the light guide plate and the light sources without being affected by expansion and contraction of the light guide plate in a direction from the light entrance planes of the light guide plate toward the light sources. 
     
     
       3. The planar lighting device of  claim 1 , wherein the sliding mechanisms each further comprise another pin provided on the housing engaged in a circular hole formed at the center of the light source, the long holes being disposed on the sides of the circular hole, the light source being freely expand and contract evenly from the center defined by the circular hole. 
     
     
       4. The planar lighting device of  claim 1 , further comprising pins provided on the housing engaged in long holes formed in the light guide plate so as to be long in the direction parallel to the light entrance planes, the light guide plate being freely expand and contract in the direction parallel to the light entrance planes. 
     
     
       5. A planar lighting device comprising:
 a light guide plate including a concave rectangular light exit plane, two light entrance planes containing two opposite sides of the light exit plane and disposed opposite each other, two symmetrical inclined planes opposing to the light exit plane such that their distance from the light exit plane increases such that their distance from the light exit plane increases with the increasing distance from the two light entrance planes toward the center of the light exit plane, a curved portion connection the two inclined planes, and light scattering particles for scattering light that propagates inside the light guide plate; 
 two light sources respectively disposed opposite the two light entrance planes for emitting light to enter the light into the light guide plate through the light entrance planes; 
 holder means for supporting and integrating each light source and the light guide plate while keeping their mutual distance constant, 
 a housing for accommodating the light sources and the light guide plate integrated by the holder means; and 
 sliding mechanisms allowing the light sources to slide in a direction parallel to the light entrance planes of the light guide plate to absorb the expansion and contraction of the light sources along the length thereof, 
 wherein the light guide plate has a minimum thickness of 0.5 mm to 3.0 mm both inclusive at the light entrance planes, a maximum thickness of 1.0 mm to 6.0 mm both inclusive at a center of the curved portion, the curved portion having a radius of curvature of 1500 mm to 45000 mm both inclusive, the inclined planes each forming a taper angle of 0.1° to 2.2° both inclusive with respect to a line parallel to the light exit plane. 
 
     
     
       6. A planar lighting device comprising:
 a light guide plate including a concave rectangular light exit plane, two light entrance planes containing two opposite sides of the light exit plane and disposed opposite each other, two symmetrical inclined planes opposing to the light exit plane such that their distance from the light exit plane increases with the increasing distance from the two light entrance planes toward the center of the light exit plane, a curved portion connecting the two inclined planes, and light scattering particles for scattering light that propagates inside the light guide plate; 
 two light sources respectively disposed opposite the two light entrance planes for emitting light to enter the light into the light guide plate through the light entrance planes; 
 holder means for supporting and integrating each light source and the light guide plate while keeping their mutual distance constant; 
 a housing for accommodating the light sources and the light guide plate integrated by the holder means; and 
 sliding mechanisms allowing the light sources to slide in a direction parallel to the light entrance planes of the light guide plate to absorb the expansion and contraction of the light sources along the length thereof, 
 wherein the light exit plane of the light guide plate is formed of a curved plane curved toward the inclined planes, and has a radius of curvature of 55000 mm to 120000 mm both inclusive, the curved portion having a radius of curvature of 10000 mm to 55000 mm both inclusive.